U.S. patent application number 11/618924 was filed with the patent office on 2007-07-12 for compact hydraulic actuator system.
Invention is credited to Xinhua He.
Application Number | 20070157612 11/618924 |
Document ID | / |
Family ID | 37908119 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070157612 |
Kind Code |
A1 |
He; Xinhua |
July 12, 2007 |
COMPACT HYDRAULIC ACTUATOR SYSTEM
Abstract
A hydraulic actuator, comprising: a housing; a rod secured to a
piston, the rod and piston being slidably received within the
housing, wherein the rod along with the piston is capable of
movement between a first position and a second position; a first
chamber positioned on one side of the piston and within the
housing; a second chamber positioned on another side of the piston
and within the housing; a self contained flexible volume
compensator disposed within the housing; a fluid disposed in the
first chamber, the second chamber and the self contained flexible
volume compensator, wherein the fluid in the self contained
flexible volume compensator is pressurized to a predetermined
pressure level; a bidirectional pump for moving the fluid between
the first chamber, the second chamber and the self contained
flexible volume compensator; a valve system disposed in the housing
and for providing selective fluid communication between the first
chamber, the second chamber and the self contained flexible volume
compensator as the rod moves in a range of movement defined by the
first position and the second position, wherein the valve system
isolates the first chamber from the self contained flexible volume
compensator and the second chamber when a fluid pressure in at
least one of the first chamber, the second chamber and the self
contained flexible volume compensator is below a predetermined
level; and wherein the pressurized fluid in the self contained
flexible volume compensator is transferred from the self contained
flexible volume compensator to the second chamber via the pump and
fluid in the first chamber is transferred to pump from the first
chamber when the rod is moved toward the second position and
wherein fluid in the second chamber is transferred from second
chamber to the self contained flexible volume compensator and the
first chamber when the rod and piston are moved towards the first
position.
Inventors: |
He; Xinhua; (Troy,
MI) |
Correspondence
Address: |
DELPHI TECHNOLOGIES, INC.
M/C 480-410-202, PO BOX 5052
TROY
MI
48007
US
|
Family ID: |
37908119 |
Appl. No.: |
11/618924 |
Filed: |
January 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60757663 |
Jan 10, 2006 |
|
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|
Current U.S.
Class: |
60/413 |
Current CPC
Class: |
F15B 1/265 20130101;
F15B 2211/7053 20130101; F15B 15/18 20130101; F15B 2211/20561
20130101; F15B 2211/625 20130101; F15B 2211/3051 20130101; F15B
2211/50527 20130101; F15B 2211/212 20130101; F15B 1/02
20130101 |
Class at
Publication: |
60/413 |
International
Class: |
F16D 31/02 20060101
F16D031/02 |
Claims
1. A hydraulic actuator, comprising: a housing; a rod secured to a
piston, the rod and piston being slidably received within the
housing, wherein the rod along with the piston is capable of
movement between a first position and a second position; a first
chamber positioned on one side of the piston and within the
housing; a second chamber positioned on another side of the piston
and within the housing; a self contained flexible volume
compensator disposed within the housing; a fluid disposed in the
first chamber, the second chamber and the self contained flexible
volume compensator, wherein the fluid in the self contained
flexible volume compensator is pressurized to a predetermined
pressure level; a bidirectional pump for moving the fluid between
the first chamber, the second chamber and the self contained
flexible volume compensator; a valve system disposed in the housing
and for providing selective fluid communication between the first
chamber, the second chamber, the pump and the self contained
flexible volume compensator as the rod moves in a range of movement
defined by the first position and the second position, wherein the
valve system isolates the first chamber from the self contained
flexible volume compensator and the second chamber when a fluid
pressure in at least one of the first chamber, the second chamber
and the self contained flexible volume compensator is below a
predetermined level; and wherein the pressurized fluid in the self
contained flexible volume compensator is transferred from the self
contained flexible volume compensator to the second chamber via the
pump and fluid in the first chamber is transferred to the pump from
the first chamber when the rod is moved toward the second position
and wherein fluid in the second chamber is transferred from the
second chamber to the self contained flexible volume compensator
and the first chamber when the rod and piston are moved towards the
first position.
2. The hydraulic actuator as in claim 1, wherein substantially no
fluid passes through the piston as the rod moves between the first
position and the second position.
3. The hydraulic actuator as in claim 1, wherein the first position
corresponds to the rod being fully retracted within the housing and
the second position corresponds to the rod being fully extracted
from the housing and wherein the rod passes through an opening in
the housing and the first chamber is disposed between the piston
and the opening.
4. The hydraulic actuator as in claim 1, wherein the hydraulic
actuator further comprises an inner cylinder, wherein the piston,
the first chamber and the second chamber are disposed within the
inner cylinder and the self contained flexible volume compensator
is disposed between an outer surface of the inner cylinder and an
inner surface of the housing, wherein the self contained flexible
volume compensator is pre-pressurized to a predetermined level that
is higher than one atmosphere but less than a pressure required to
urge the piston and the rod between the first and second
positions.
5. The hydraulic actuator as in claim 4, wherein the rod is a
hollow cylinder and the hydraulic actuator further comprises a
sensor positioned within the rod, wherein the sensor is configured
to measure movement of the hollow cylinder, wherein the sensor
outputs a signal indicative of a position of the rod within the
housing and fluid in the first chamber is transferred from the
first chamber when the rod is moved toward the second position by
overcoming a first valve of a first subassembly and a first valve
of a second subassembly, the first valve of the first subassembly
providing selective fluid communication between the first chamber
and the second chamber and the first valve of the second
subassembly providing selective fluid communication between the
second chamber and the self contained flexible volume compensator
and the first chamber and wherein the pressurized fluid in the self
contained flexible volume compensator is transferred from the self
contained flexible volume compensator to the second chamber and
fluid in the second chamber is transferred to the self contained
flexible volume compensator and the first chamber from the second
chamber when the rod is moved towards the first position by
overcoming a second valve of the first subassembly and a second
valve of the second subassembly, the second valve of the first
subassembly providing selective fluid communication between the
first chamber and the second chamber and the second valve of the
second subassembly providing selective fluid communication between
the second chamber and the self contained flexible volume
compensator.
6. The hydraulic actuator as in claim 5, wherein the fluid in the
self contained flexible volume compensator is pre-pressurized by a
pressure means and the valve system further comprises a cross over
relief module for manual operation of the hydraulic actuator.
7. The hydraulic actuator as in claim 6, wherein the pressure means
is a spring applying a force to a compressible portion of the
flexible volume compensator and substantially no air is in the
first chamber, the second chamber, the pump, the self contained
flexible volume compensator and the valve system.
8. The hydraulic actuator as in claim 4, wherein a maximum volume
of the second chamber is defined when the rod and piston are at the
second position and a maximum volume of the first chamber is
defined when the rod and piston are at the first position, wherein
the maximum volume of the second chamber is greater than the
maximum volume of the first chamber.
9. The hydraulic actuator as in claim 8, wherein the first position
corresponds to the rod being fully retracted within the housing and
wherein the second position corresponds to the rod being fully
extracted from the housing.
10. The hydraulic actuator as in claim 9, wherein the housing is
linear in shape and substantially no air is in the first chamber,
the second chamber, the pump and the self contained flexible volume
compensator.
11. The hydraulic actuator as in claim 5, further comprising a
control unit configured to receive signals from the sensor and
operate the bidirectional pump, wherein the piston has an opening
that allows a portion of the sensor to pass therethrough and into
the rod as the rod moves between the first and second positions and
wherein substantially no fluid passes through the piston as the rod
moves between the first position and the second position and
wherein the sensor comprises a variable resistor and a movable
contact of the sensor is secured to either the rod or the
piston.
12. The hydraulic actuator as in claim 8, wherein the rod is
secured to either a door or a body of a vehicle and the housing is
secured to either the door or the body of the vehicle.
13. The hydraulic actuator as in claim 8, wherein the
pre-pressurized fluid in the self contained flexible volume
compensator assists in moving the rod in the range of movement.
14. A method for actuating a rod of a hydraulic actuator,
comprising: pressurizing a fluid in a self contained flexible
volume compensator of the hydraulic actuator; and displacing a
portion of the fluid of the self contained flexible volume
compensator into a second chamber of the hydraulic actuator as a
rod of the hydraulic actuator moves from a first position towards a
second position wherein a piston coupled to the rod increases a
volume of the second chamber and decreases a volume of a first
chamber, wherein a portion of a fluid in the second chamber is
transferred to the self contained flexible volume compensator when
the rod moves from the second position to the first position, and
wherein the self contained flexible volume compensator, the first
chamber and the second chamber are disposed within a housing of the
hydraulic actuator and a valve system disposed in the housing
provides selective fluid communication between the first chamber,
the second chamber and the self contained flexible volume
compensator as the rod moves in a range of movement defined by the
first position and the second position, wherein the valve system
isolates the first chamber from the self contained flexible volume
compensator and the second chamber when a fluid pressure in at
least one of the first chamber, the second chamber and the self
contained flexible volume compensator is below a predetermined
level.
15. The method as in claim 14, wherein the hydraulic actuator
further comprises a bidirectional pump disposed within the housing
for displacing the fluid between the first chamber, the second
chamber and the self contained flexible volume compensator, wherein
the self contained flexible volume compensator is pre-pressurized
to a predetermined level that is higher than one atmosphere but
less than a pressure required to urge the piston between the first
and second positions and wherein fluid from the first chamber does
not directly flow into the self contained flexible volume
compensator.
16. The method as in claim 15, wherein the hydraulic actuator
further comprises an inner cylinder, wherein the piston, the first
chamber and the second chamber are disposed within the inner
cylinder and the self contained flexible volume compensator is
disposed between an outer surface of the inner cylinder and an
inner surface of the housing and the housing is cylindrical in
shape.
17. The method as in claim 15, further comprising: measuring
movement of the rod within the housing with a sensor disposed
inside the rod, the sensor being a transducer configured to provide
a plurality of signals corresponding to the movement of the rod
within the housing, wherein the plurality of signals are received
by a control unit configured to operate the bidirectional pump
based upon the plurality of signals provided by the transducer and
wherein the fluid in the self contained flexible volume compensator
is pre-pressurized by a pressure means, wherein the piston has an
opening that allows a portion of the sensor to pass therethrough
and into the rod as the rod moves between the first and second
positions and wherein substantially no fluid passes through the
piston as the rod moves between the first position and the second
position and wherein the sensor comprises a variable resistor and a
movable contact of the sensor is secured to either the rod or the
piston.
18. A hydraulic actuator, comprising: a linear housing; an inner
cylinder disposed within the linear housing; a rod secured to a
piston, the rod and piston being slidably received within the inner
cylinder, wherein the rod along with the piston is capable of
movement between a first position and a second position; a first
chamber defined by the inner cylinder and the piston, the first
chamber being positioned on one side of the piston; a second
chamber defined by the inner cylinder and the piston, the second
chamber being positioned on another side of the piston; a self
contained flexible volume compensator disposed between an exterior
surface of the inner cylinder and an inner surface of the housing;
a fluid disposed in the first chamber, the second chamber and the
self contained flexible volume compensator, wherein the fluid in
the self contained flexible volume compensator is pressurized to a
predetermined pressure level; a bidirectional pump for moving the
fluid between the first chamber, the second chamber and the self
contained flexible volume compensator; a valve system disposed in
the housing and for providing selective fluid communication between
the first chamber, the second chamber, the pump and the self
contained flexible volume compensator as the rod moves in a range
of movement defined by the first position and the second position,
wherein the valve system isolates the first chamber from the self
contained flexible volume compensator and the second chamber when a
fluid pressure in at least one of the first chamber, the second
chamber and the self contained flexible volume compensator is below
a predetermined level; and wherein the pressurized fluid in the
self contained flexible volume compensator is transferred from the
self contained flexible volume compensator to the second chamber
and fluid in the first chamber is transferred to the pump from the
first chamber when the rod is moved toward the second position by
overcoming a first valve of a first subassembly and a first valve
of a second subassembly, the first valve of the first subassembly
providing selective fluid communication between the first chamber
and the pump or the second chamber and the first valve of the
second subassembly providing selective fluid communication between
the second chamber and the self contained flexible volume
compensator and the first chamber wherein the fluid in the second
chamber is transferred to the self contained flexible volume
compensator and the first chamber from the second chamber when the
rod is moved towards the first position by overcoming a second
valve of the first subassembly and a second valve of the second
subassembly, the second valve of the first subassembly providing
selective fluid communication between the first chamber and the
second chamber and the second valve of the second subassembly
providing selective fluid communication between the second chamber
and the self contained flexible volume compensator.
19. The hydraulic actuator as in claim 18, wherein the first valve
of the first subassembly is a counterbalance valve and the first
valve of the second subassembly is a check valve.
20. The hydraulic actuator as in claim 19, wherein the second valve
of the first subassembly is a check valve and the second valve of
the second subassembly is a counter balance valve and the first
subassembly further comprises a first pilot check valve and the
second subassembly further comprises a first pilot check valve,
wherein the first pilot check valve of the first subassembly and
the second subassembly are configured to provide selective fluid
communication between the self contained flexible volume
compensator and the check valves of the first and second
subassemblies.
21. The hydraulic actuator as in claim 20, wherein the self
contained flexible volume compensator is pre-pressurized to a
predetermined level that is higher than one atmosphere but less
than a pressure required to urge the piston and the rod between the
first and second positions.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. Provisional Patent
Application Ser. No. 60/757,663 filed Jan. 10, 2006, the contents
of which are incorporated herein by reference thereto.
BACKGROUND
[0002] Exemplary embodiments of the present invention relate to a
hydraulic system. More particularly, exemplary embodiments of the
present invention relate to an apparatus and method for providing a
compact hydraulic system.
[0003] Hydraulic actuators are commonly found in many engineered
systems for a wide range of applications, including military,
space, aerospace, and many industrial applications. Generally, a
hydraulic system includes some elements such as a pump, a fluid
supplier (reservoir), a connecting piping system, a closed
hydraulic cylinder, and necessary control valves, etc. An
electrical motor is commonly used to drive the hydraulic pump to
pressurize the fluid for function. Traditionally, those elements of
the hydraulic system are designed as sub-system and/or
sub-components that are not fully integrated into a single
system.
[0004] Moreover, hydraulic systems also require a reservoir. The
reservoir is often separated from the pump and the cylinder of the
hydraulic actuator and they are connected through hoses or tubes.
Typically, the reservoir functions as fluid supplier and fluid
storage. The pump receives fluid from the reservoir when the
cylinder of the actuator is extending and sends fluid back to the
reservoir during retraction of the cylinder or a rod associated
with the system.
[0005] Typically, the reservoir usually is not contained as it
needs to be open to atmosphere and consists of a free volume with
air getting in and out of the reservoir during the operation. In
such systems, the location and orientation of the reservoir is
limited as it must be located above the pump so that the fluid can
only flow down by gravity during the operation, and to prevent air
from getting into the pump and cylinder during the operation.
[0006] In these systems the reservoir is preferably vertically
oriented in order to prevent fluid from getting out the reservoir
during the operation.
[0007] Accordingly, some disadvantages of these hydraulic actuators
are that the system is not compact, connecting pipes are required
and provide potential areas for leakage, and the reservoir itself
must be oriented and installed to compensate for the effects of
gravity on the reservoir.
[0008] Accordingly, it is desirable to provide a compact integrated
hydraulic actuator system.
SUMMARY OF THE INVENTION
[0009] This disclosure relates to an apparatus and method for a
compact hydraulic system.
[0010] In one exemplary embodiment, a hydraulic actuator is
disclosed, the hydraulic actuator comprising: a housing; a rod
secured to a piston, the rod and piston being slidably received
within the housing, wherein the rod along with the piston is
capable of movement between a first position and a second position;
a first chamber positioned on one side of the piston and within the
housing; a second chamber positioned on another side of the piston
and within the housing; a self contained flexible volume
compensator disposed within the housing; a fluid disposed in the
first chamber, the second chamber and the self contained flexible
volume compensator, wherein the fluid in the self contained
flexible volume compensator is pressurized to a predetermined
pressure level; a bidirectional pump for moving the fluid between
the first chamber, the second chamber and the self contained
flexible volume compensator; a valve system disposed in the housing
and for providing selective fluid communication between the first
chamber, the second chamber and the self contained flexible volume
compensator as the rod moves in a range of movement defined by the
first position and the second position, wherein the valve system
isolates the first chamber from the self contained flexible volume
compensator and the second chamber when a fluid pressure in at
least one of the first chamber, the second chamber and the self
contained flexible volume compensator is below a predetermined
level; and wherein the pressurized fluid in the self contained
flexible volume compensator is transferred from the self contained
flexible volume compensator to the second chamber via the pump and
fluid in the first chamber is transferred to pump from the first
chamber when the rod is moved toward the second position and
wherein fluid in the second chamber is transferred from second
chamber to the self contained flexible volume compensator and the
first chamber when the rod and piston are moved towards the first
position.
[0011] In another exemplary embodiment, a method for actuating a
rod of a hydraulic actuator is provided the method comprising:
pressurizing a fluid in a self contained flexible volume
compensator of the hydraulic actuator; and displacing a portion of
the fluid of the self contained flexible volume compensator into a
second chamber of the hydraulic actuator as a rod of the hydraulic
actuator moves from a first position towards a second position
wherein a piston coupled to the rod increases a volume of the
second chamber and decreases a volume of a first chamber, wherein a
portion of a fluid in the second chamber is transferred to the self
contained flexible volume compensator when the rod moves from the
second position to the first position, and wherein the self
contained flexible volume compensator, the first chamber and the
second chamber are disposed within a housing of the hydraulic
actuator and a valve system disposed in the housing provides
selective fluid communication between the first chamber, the second
chamber and the self contained flexible volume compensator as the
rod moves in a range of movement defined by the first position and
the second position, wherein the valve system isolates the first
chamber from the self contained flexible volume compensator and the
second chamber when a fluid pressure in at least one of the first
chamber, the second chamber and the self contained flexible volume
compensator is below a predetermined level.
[0012] In another exemplary embodiment a hydraulic actuator is
provided, the hydraulic actuator comprising: a linear housing; an
inner cylinder disposed within the linear housing; a rod secured to
a piston, the rod and piston being slidably received within the
inner cylinder, wherein the rod along with the piston is capable of
movement between a first position and a second position; a first
chamber defined by the inner cylinder and the piston, the first
chamber being positioned on one side of the piston; a second
chamber defined by the inner cylinder and the piston, the second
chamber being positioned on another side of the piston; a self
contained flexible volume compensator disposed between an exterior
surface of the inner cylinder and an inner surface of the housing;
a fluid disposed in the first chamber, the second chamber and the
self contained flexible volume compensator, wherein the fluid in
the self contained flexible volume compensator is pressurized to a
predetermined pressure level; a bidirectional pump for moving the
fluid between the first chamber, the second chamber and the self
contained flexible volume compensator; a valve system disposed in
the housing and for providing selective fluid communication between
the first chamber, the second chamber, the pump and the self
contained flexible volume compensator as the rod moves in a range
of movement defined by the first position and the second position,
wherein the valve system isolates the first chamber from the self
contained flexible volume compensator and the second chamber when a
fluid pressure in at least one of the first chamber, the second
chamber and the self contained flexible volume compensator is below
a predetermined level; and wherein the pressurized fluid in the
self contained flexible volume compensator is transferred from the
self contained flexible volume compensator to the second chamber
and fluid in the first chamber is transferred to the pump from the
first chamber when the rod is moved toward the second position by
overcoming a first valve of a first subassembly and a first valve
of a second subassembly, the first valve of the first subassembly
providing selective fluid communication between the first chamber
and the pump or the second chamber and the first valve of the
second subassembly providing selective fluid communication between
the second chamber and the self contained flexible volume
compensator and the first chamber wherein the fluid in the second
chamber is transferred to the self contained flexible volume
compensator and the first chamber from the second chamber when the
rod is moved towards the first position by overcoming a second
valve of the first subassembly and a second valve of the second
subassembly, the second valve of the first subassembly providing
selective fluid communication between the first chamber and the
second chamber and the second valve of the second subassembly
providing selective fluid communication between the second chamber
and the self contained flexible volume compensator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross sectional view of a hydraulic actuator
constructed in accordance with an exemplary embodiment of the
present invention;
[0014] FIG. 2 is a cross sectional perspective view of a compact
actuator constructed in accordance with an exemplary embodiment of
the present invention;
[0015] FIG. 2A is an enlarged partial cross sectional view of a
portion of an exemplary embodiment of the present invention;
[0016] FIG. 2B is a schematic illustration of a sensor/transducer
of an alternative exemplary embodiment of the present
invention;
[0017] FIG. 3 is a cross sectional schematic view of a hydraulic
actuator constructed in accordance with an exemplary embodiment of
the present invention;
[0018] FIG. 4 is a schematic illustration of a hydraulic actuator
and control scheme in accordance with an exemplary embodiment of
the present invention;
[0019] FIG. 5 is a schematic illustration of a hydraulic actuator
and control scheme in accordance with another exemplary embodiment
of the present invention;
[0020] FIG. 6 is a perspective view of a compact actuator
constructed in accordance with an exemplary embodiment of the
present invention;
[0021] FIG. 7 is a cross sectional schematic view of a hydraulic
actuator constructed in accordance with another exemplary
embodiment of the present invention;
[0022] FIG. 8 is a cross sectional schematic view of a hydraulic
actuator constructed in accordance with yet another exemplary
embodiment of the present invention; and
[0023] FIG. 9 illustrates the hydraulic actuator in a vehicle.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0024] Exemplary embodiments of the present invention relate to an
integrated, self-contained, compact in-line hydraulic system. In
one exemplary embodiment, the modular compact in-line hydraulic
system is used as an actuator for automotive applications, such as
driving a side door, tail gate, sliding door, deck lit, etc. In
another exemplary embodiment, the modular compact in-line hydraulic
system can also be used as a driving device for many other
industrial fields where a compact in-line actuator system is
desired, such as medical machines, health and sport training
machines, assembly stations or lines, testing machines, lifting or
actuating units in aerospace industries, etc.
[0025] Referring now to FIGS. 1-3 a hydraulic actuator 10 in
accordance with an exemplary embodiment of the present invention is
illustrated. In accordance with an exemplary embodiment of the
present invention, hydraulic actuator 10 comprises an integrated,
self contained, compact in-line hydraulic system. Hydraulic
actuator 10 includes an electrical motor 12 disposed in a motor
housing 14. The electric motor is coupled to a hydraulic pump 16
disposed in a pump housing 18, wherein the pump housing is secured
to the motor housing. Many types of fluid pumps can be used in
exemplary embodiments of the present invention. Some pumps include
but are not limited to gear pumps, piston pumps, screw type pumps,
or vane pumps, etc. Pump 16 is configured to provide fluid to a
plurality of valve modules 20 and 22, which are disposed within an
actuator housing or closed hydraulic cylinder 24. In accordance
with an exemplary embodiment the fluid is a hydraulic fluid or any
other suitable fluid having characteristics suitable for use in
exemplary embodiments of the present invention. In accordance with
an exemplary embodiment valve modules 20 and 22 are in fluid
communication with the pump and chambers of the hydraulic actuator
through optional transition plates 19 and 21. As will be discussed
herein the transition plates will be used with an optional sensor
system for determining the movement of the rod within the housing.
Alternatively, and if the optional sensor system requiring the
transition plates is not used there will be no need for the
transition plates. In yet another alternative embodiment, the
actuator may be configured to have a sensor that does not require a
transition plate. Although motor housing 14, pump housing 18 and
actuator housing 24 are shown as separate items secured together it
is understood that alternative exemplary embodiments contemplate a
single or two housing structures for housing each of the components
being secured together in a linear fashion.
[0026] Disposed within actuator housing or closed hydraulic
cylinder 24 is an inner cylinder 25 defining a chamber for slidably
receiving an output rod 26 that has a piston 28 at one end and an
actuation end 29 at the other. The output rod is configured to move
within a sealed opening 30 of an end cap 32 as piston 28 moves
within a chamber 34 of cylinder 25. As shown, piston 28 is
configured to provide a seal between chambers 42 and 44 via a seal
ring 35 or a plurality of seal rings disposed about the periphery
of the piston so that substantially no fluid from the first chamber
may leak directly into the second chamber through the piston and
vice versa as the piston moves within the chamber 34 of cylinder
25. In one non-limiting exemplary embodiment and as illustrated in
FIG. 2A the seal ring is a Teflon material disposed about the
periphery of the piston. In another embodiment, the seal ring
comprises a copper material or copper alloy or equivalent thereof.
In another alternative exemplary embodiment, an O-ring 37 may be
used in conjunction with the seal ring wherein the O-ring is
disposed between the seal ring and the piston by for example, the
O-ring and the seal ring may be disposed in a groove 39 located on
the surface of the piston. In addition, a stable device, guide
device or wear ring or a plurality of wear rings 41 may be disposed
about the piston and at either side of the seal ring to prevent
rotation and twisting of the piston as the piston and rod move
within the housing. This will prevent the piston from being
angularly displaced, which may damage the housing and the seal
about the rod. In addition, the guide device will ensure a more
accurate sensing of the piston as it moves in the cylinder.
[0027] In accordance with one exemplary embodiment cylinder 25 and
accordingly chamber 34 is configured to be positioned within
actuator housing 24 so that a compensator or compensation chamber
or self-contained flexible volume compensator 36 is disposed
between an exterior surface 38 of the cylinder 25 and an interior
surface 40 of the actuator housing or closed hydraulic cylinder 24
thus providing a compensator 36 that surrounds or partially
surrounds cylinder 25. In one exemplary embodiment, the compensator
provides a portion of the flow path between the first and second
chambers thus additional flow conduits are not required. In
accordance with an exemplary embodiment a first chamber 42 is
disposed on one side of the piston and a second chamber 44 is
positioned on the other side of the piston as the piston moves
linearly within chamber 34. In accordance with an exemplary
embodiment and as the rod moves into and out of the actuator
housing the volume or size of the first and second chambers will
vary accordingly. This is due to the corresponding movement of
piston 28 as rod 26 moves therein.
[0028] In accordance with an exemplary embodiment of the present
invention, the first chamber is in selective fluid communication
with the compensation chamber and the second chamber via a valve
system 46 disposed within the plurality of valve modules and the
housings/cylinders. In accordance with an exemplary embodiment the
valve system comprises a plurality of valves and flow channels. As
will be discussed herein, a first valve subassembly 45 will provide
selective fluid communication between the self-contained flexible
volume compensator 36, pump 14, and the first chamber 42 while a
second valve subassembly 47 will provide selective fluid
communication between the self-contained flexible volume
compensator 36, pump 14 and the second chamber 44. In accordance
with an exemplary embodiment of the present invention and as will
be discussed herein first valve subassembly 45 comprises a
counterbalance valve, a check valve and a pilot check valve some of
which are configured to provide fluid flow in one direction only.
Of course and as applications require, other types of valve
mechanisms may be employed. In addition and in accordance with an
exemplary embodiment of the present invention second valve
subassembly will also comprise a counterbalance valve, a check
valve and a pilot check valve some of which are configured to
provide fluid flow in one direction only. Again, other types of
valve mechanisms may be employed.
[0029] Accordingly and in accordance with an exemplary embodiment,
the motor is coupled to a control unit 48 wherein operational
signals are provided to energize the motor that drives the pump to
pump fluid to and from the first chamber, the second chamber and
the self contained flexible volume compensator to manipulate the
position of the output rod. In accordance with an exemplary
embodiment of the present invention, the control unit or control
module may be located within the actuator or remotely located as
long as the operational signals to and from the control unit are
capable of being received and transmitted.
[0030] In addition, and as an alternative exemplary embodiment a
sensor 50 is provided to provide signals indicative of the movement
of the output rod to the control unit wherein the signals are used
to energize or de-energize the motor corresponding to the position
of the output rod. In accordance with an exemplary embodiment the
sensor is a transducer or variable resistor configured to track the
movement or presence of the output rod and provide a signal
indicative of the rod's position back to the control unit. In
accordance with an exemplary embodiment sensor 50 is a
potentiometer or variable resistor wherein a pot is used to as the
primary choice of transducer for converting mechanical position of
the rod and/or piston into an electrical signal that can be used by
the controller. In accordance with an exemplary embodiment and as
the rod and cylinder move the setting (and the resistance) of the
pot is being changed.
[0031] As is known in the related arts and as illustrated
schematically in FIG. 2B a pot generally has three wires R, W, B or
terminals. Two are simply the connections to the ends of the
resistive element. The remaining terminal connects to a moveable
contact called the wiper 43. The wiper slides along the surface of
the resistive element as the rod is moved and in an exemplary
embodiment, the wiper is conductive and provides a conductive path
between the resistive element and a wire. As the wiper is moved
closer to one end of the resistive element, the resistance between
the wiper terminal and that end terminal decreases thus, a signal
(e.g., voltage from a power source) indicative of the position of
the rod is capable of being generated. In one non-limiting
exemplary embodiment, the wiper is secured to the piston and as the
same moves along the two other wires a signal indicative of the
position of the rod is generated.
[0032] For example and in one exemplary embodiment, the rod 26 is
configured to have a hollow chamber 51 in which the
transducer/sensor is positioned such that movement of the rod will
be tracked by the sensor and a signal is outputted to the control
unit wherein the signal is indicative of the movement of the rod.
In this exemplary embodiment, the piston is configured to have an
opening 53, which allows the transducer to extend into the hollow
chamber 51, the wires of the transducer to extend through opening
53 into the transition plate and ultimately to the control unit
while the third or slider providing the electrical bridge is
secured to the piston and/or interior of the rod and the position
of the rod via the slider determines what percentage of an input
voltage will be applied to the circuit of the sensor. Although
opening 53 allows access to the hollow chamber 51 of the rod from
chamber 44 it is understood that substantially no fluid passes
directly from the first chamber to the second chamber through the
rod and opening 53. Of course, other types of sensing devices may
be employed. For example, one other non-limiting sensor is linear
position sensor or linear variable differential transformer, or
LVDT, wherein a series of inductors are positioned in a hollow
cylindrical shaft and a solid cylindrical core is provided. As is
known in the related arts a LVDT will produce an electrical output
proportional to the position of the core. In one example, two
secondary coils are placed symmetrically on either side of a
primary coil contained within the hollow cylindrical shaft.
Movement of the magnetic core causes the mutual inductance of each
secondary coil to vary relative to the primary, and thus the
relative voltage induced from the primary coil to the secondary
coil will vary as well. Non-limiting examples of such a sensor may
be found at http://www.macrosensors.com. In an exemplary
embodiment, the core will be secured to the transition plate and
the hollow shaft will vary the position of the coils with respect
to the core.
[0033] In accordance with an exemplary embodiment the control unit
will comprise a controller comprising a microcontroller,
microprocessor, or other equivalent processing device capable of
executing commands of computer readable data or program for
executing a control algorithm. In order to perform the prescribed
functions and desired processing, as well as the computations
therefore (e.g., operating the motor and pump), the controller may
include, but not be limited to, a processor(s), computer(s),
memory, storage, register(s), timing, interrupt(s), communication
interfaces, and input/output signal interfaces, as well as
combinations comprising at least one of the foregoing. For example,
the controller may include input signal filtering to enable
accurate sampling and conversion or acquisitions of such signals
from communications interfaces. As described above, exemplary
embodiments of the present invention can be implemented through
computer-implemented processes and apparatuses for practicing those
processes.
[0034] In accordance with an exemplary embodiment of the present
invention all of the sub-systems and components may be modulated
and integrated as a single unit, which has a cylindrical housing of
an extended linear configuration. The integration and assembly may
vary based upon applications. For example, the hydraulic cylinder
may comprise the flexible compensator, the first and second
chambers, the transition plates, the control module, which is
secured to a pump module and a motor module.
[0035] In accordance with an exemplary embodiment the elements are
all designed and arranged in-line with the hydraulic cylinder so
that a compact package, particularly compact in diameter, can be
achieved. The compact in-line hydraulic system with optional
modules may be assembled together within a tube-like housing.
[0036] Valve system 46 includes a plurality of fluid flow channels
and ports among the pump, control units, and the flexible volume
device. The valve system is designed so that channels and ports may
be connected through the parallel surfaces. The selection of
integrated-modulated hydraulic units may be optional and
exchangeable based upon the application requirements.
[0037] The control modules or valve modules comprise various
hydraulic valve(s), which may be designed and integrated into the
control modules. The functions of the control valves and/or
module(s) may include, but not limited to, a counterbalance module,
a cross over relief module, and a pilot check module, etc. In
accordance with an exemplary embodiment of the present invention it
is also contemplated to use solenoid driven valve(s), and/or
switch(es) in conjunction with the valve system.
[0038] In accordance with an exemplary embodiment, the self
contained flexible volume device is pre-loaded or pre-pressurized
to a predetermined pressure. The means to pre-load, or pre-pressure
the flexible volume device include, but are not limited to, spring
loading the compensator, an accumulator with compressed air, or a
pressurized bladder made from rubber-like materials. In one
exemplary embodiment, the bladder is a flexible rubber like
material 55 (FIG. 4) and the bladder is inserted between the inner
cylinder and the outer housing and a spring 57 is positioned to
maintain a pre-determined amount of pressure upon the bladder. In
this embodiment no gas or air is found in the self contained
flexible volume device. In addition and in accordance with
exemplary embodiments of the present invention the hydraulic
actuator is sealed and self contained so that no air or gas is
found in the first chamber, the second chamber, the pump and the
valve system or systems interconnecting each of the components thus
in accordance with exemplary embodiments of the present invention
only the self contained flexible volume device may have compressed
air therein, which is provided only to maintain the fluid in the
self contained flexible volume device at a predetermined positive
pressure and this air does not escape into other portions of the
actuator. Again and as mentioned above, other embodiments
contemplate pressurizing the self contained flexible volume device
wherein no gas or air is in the system at all other than perhaps an
external pressure to a flexible compensator.
[0039] In accordance with an exemplary embodiment the hydraulic
actuator has a self-contained flexible volume compensator. The
self-contained flexible volume compensator balances the volume
between the first chamber and the second chamber. In accordance
with an exemplary embodiment the volume compensator is pre-loaded,
or pre-pressurized by means of spring load, compressed air, which
may be external or internal to the self-contained flexible volume
compensator wherein a low positive pressure (e.g., approximately
100 psi) in the self-contained flexible volume compensator is
provided to have selective fluid communication with at least one
chamber being at a high pressure in order to facilitate movement of
the piston and rod. In another alternative exemplary embodiment,
the self-contained flexible volume compensator is a flexible
bladder made from rubber-like materials, etc. In accordance with an
exemplary embodiment the pressurized volume compensator is
self-contained and not open to the atmosphere. In accordance with
an exemplary embodiment of the present invention, the
self-contained flexible volume compensator is pre-pressurized to a
low pressure, which in one exemplary embodiment is less than 100
psi but greater that 1 atmosphere, although pressures greater or
less than 100 psi are also contemplated and the active chamber or
chamber (e.g., first chamber 42 or second chamber 44) forcing the
movement of the piston is pressurized to a high pressure e.g.,
300-3000 psi in order to facilitate the movement of the piston and
rod within the chamber. In other words, the first and second
chambers are and associated valves are configured for high
pressures to facilitate movement while the self-contained flexible
volume compensator is pre-pressurized to at least a low pressure
respective to the high pressure chamber, which allows transfer of
fluid into the self-contained flexible volume compensator as well
as transfer of fluid out of the self-contained flexible volume
compensator.
[0040] Accordingly, and as the actuator is operated the pressurized
volume compensator will push fluid out of the volume compensator
into the pump when the cylinder and rod is extending and the fluid
will be pumped back into the volume compensator when the cylinder
and rod is retracted regardless of the location and/or orientation
of the volume compensator since it is pre-pressurized and
self-sealed. Accordingly, the self-contained flexible volume
compensator may be located anywhere between modules, such as
between the cylinder and valves, or between the valves and pump
module. It can also be located between an inner housing defining
the first chamber and the second chamber and the outer housing the
inner housing is located in. In accordance with an exemplary
embodiment the volume compensator can also function as an
accumulator with ability to provide an output as self-assistance to
the actuation of the device. In accordance with an exemplary
embodiment the self-contained flexible volume compensator can be
installed and operated in any orientation.
[0041] In accordance with an exemplary embodiment of the present
invention the valve system has a plurality of valves for providing
selective fluid communication among the chambers, the pump, and the
self-contained flexible volume compensator. The valve system and
the hydraulic actuator will operate in numerous modes, manual
extraction, manual retraction, powered extraction, powered
retraction and lock out.
[0042] In accordance with an exemplary embodiment of the present
invention, the closed hydraulic cylinder comprises a piston, a
plurality of flow channels, an outer tube or housing, a movable
inner tube as an output rod, an optional position or pressure
sensor system positioned within the output rod, a pair of end caps
(e.g., a top cap, a base cap, and seals). In accordance with an
exemplary embodiment a flow channel may be located between the
inner and outer tubes positioned between the top and base caps the
flow channel will connect the upper chamber and an inlet channel.
The movable tube may also be an optional inner flow channel, or as
a housing for the optional position sensor system. There may be a
stabilizing device, wherein the stable device or wear ring prevents
the piston from rotating or twisting as the piston moves within the
cylinder. In this embodiment, stable device or wear ring between
the piston and the inner wall provides piston with smooth movement
and prevents inaccuracies in the optional sensor system. The top
cap will have an opening for the output rod. The base cap will have
ports which connect with additional modulated hydraulic units. The
modulated hydraulic units comprising the pump and motor modules may
be attached to the base cap in sequence. The self-contained
flexible volume device may be located anywhere between modules,
such as between the cylinder and valves, or between the valves and
pump module.
[0043] Referring now to FIG. 4 and when it is desirable to have the
rod extend out of the cylinder in the direction of arrow 52, the
pump is pressurizing the right side or the second chamber 44 of the
cylinder. During this operation the bidirectional pump 14 causes
the pressurized fluid to flow through a top check valve 54 at the
right of FIG. 4 allowing fluid to enter the right side chamber.
This fluid pressure also opens a bottom pilot check valve 56, which
allows extra fluid flow out of the volume compensator 36 into the
pump. Note: FIG. 4 shows the self contained flexible volume
compensator as being pre-pressurized by for example a spring
biasing means 57 thus, no air is in the compensator or system.
Also, the self contained flexible volume compensator may be located
anywhere with the hydraulic actuator.
[0044] The moving piston in the direction of arrow 52 increases the
fluid pressure within the left side chamber until it reaches the
setting point of a counterbalance valve 58. Counterbalance valve 58
then opens and the fluid flows out of the left side chamber or the
first chamber through counterbalance valve 58 and into the
pump.
[0045] During retraction and when it is desirable to have the rod
retract into the cylinder in the direction of arrow 59, the pump is
pressurizing the left side or the first chamber of the cylinder.
During this operation the pressurized fluid flows through a check
valve 60 and enters the left side or the first chamber. The moving
piston increases the fluid pressure within the right side chamber
or the second chamber until it reaches the setting point of a
counterbalance valve 62. The counterbalance valve 62 then opens and
the fluid flows out of the right side chamber through it and into
the pump. The pumping fluid pressure at the left side also opens a
bottom pilot check valve 64, which allows the extra fluid out of
the right side chamber or second chamber 44 to flow into the volume
compensator as well as it is not necessary for movement of the rod
and piston in the direction of arrow 59.
[0046] In accordance with an exemplary embodiment of the present
invention and since the fluid system exclusive of the compensator
in some alternative embodiments does not have any compressible air
in it there will always be two independent sources of fluid for the
second chamber 44. Since there is no rod disposed in chamber 44 and
since the fluid is not compressible a greater amount or volume of
fluid is required to cause chamber 44 to be an active side of the
actuator. Accordingly, a greater amount of fluid is required to
move the rod and piston on the direction of arrow 52. Thus and
during this operation (e.g., in the direction of arrow 52) fluid
flows from the pump into the second chamber 44 wherein the pump is
supplied with fluid from both the compensator 36 and the first
chamber 42.
[0047] In contrast and when the rod is actuated in the direction of
arrow 59 by reversing the pump, the pilot check valve 64 opens and
the excessive fluid will flow back into the compensator as the
extra fluid from the second chamber is not necessary due to the
reduced volume caused by the presence of the rod in chamber 42. In
other words moving the piston all the way to end plate 32 will
create a greater volume in chamber 44 than a volume created in
chamber 42 when the piston is moved all the way to the opposite
plate again due to the presence of the rod in the chamber thus, the
self-contained flexible volume device or compensator 36 compensates
for the need of extra fluid in one operation and lack thereof in
another operation. Along these lines and in yet another alternative
exemplary embodiment, pilot check valve 56 may be replaced with a
one way check valve as long as the sucking pressure of the pump
will open the valve since only flow out of the compensator for
actuating the rod in the direction of arrow 52 may be required
while two way flow is required from valve 64 as the rod moves in
the directions of arrows 52 and 59.
[0048] During a hold request or position when the cylinder, rod,
and piston need to stop and hold in any position when the pump
stops and fluid is not pressurized without any flow, all check
valves and counterbalance valves will close. In this configuration
the chambers within the cylinder are disconnected and fluid cannot
flow out or into the chambers through valves. The system, thus, is
self-locked.
[0049] During a manual operation and when the cylinder, rod, and
piston need to be extended manually (e.g., when the pump stops) the
moving piston increases the fluid pressure within the left side
chamber or the first chamber until it reaches the setting point of
the counterbalance valve 58. Then the counterbalance valve 58 opens
and the fluid flows out of the left side chamber through the
counterbalance valve 58 and then the pressure also opens a middle
crossover check valve 68 comprising a portion of a cross over
relief module 49, which in accordance with an exemplary embodiment
of the present invention provides at least two functions 1) a
bypass relief when the piston has completely traveled to one side
of the chamber and the pump is still pressurizing the active
chamber and 2) a manual bypass or override when the rod is being
manipulated manually and the pump is not activated. The fluid then
flows through the middle crossover check valve 68 and the check
valve 54 into the right side chamber. The pressure also opens the
pilot check valve 56, which allows the extra fluid flows out of the
volume compensator into the right side chamber. During this manual
operation the pressurized fluid of the self contained flexible
volume compensator will assist in the extraction.
[0050] When the cylinder, rod, and piston need to be retracted
manually (e.g., when the pump stops due to operational failure or
not power or during manual operation) the moving piston increases
the fluid pressure within the right side chamber or second chamber
until it reaches the setting point of the counterbalance valve 62.
The counterbalance valve 62 then opens and the fluid flows out of
the right side chamber through it and then the pressure also opens
a middle crossover check valve 70 to open. The fluid then flows
through the middle crossover check valve 70 and the valve 60 into
the left side chamber. The pressure also opens the pilot check
valve 64, which allows the extra fluid flows into the volume
compensator from the right side chamber or second chamber.
[0051] As discussed above and as illustrated in FIGS. 1 and 3 and
in alternative exemplary embodiments of the present invention, the
system has an optional position sensor, which can be located at the
side of the cylinder, middle of the cylinder, side or center of the
rod. In this embodiment, the system may be programmable to stop and
start at any position within the operation range if required and
based upon the sensor output. In addition, the system may be
programmable to a desirable speed profile within the operation
range if required. In yet another alternative exemplary embodiment,
the system may be programmable for a manual-to-power-start feature
within the operation range if required. In other words when the
actuator is manipulated manually and the sensor detects movement a
signal is sent to the controller to activate the motor and provide
powered retraction and/or extraction of the rod.
[0052] Referring now to FIG. 5 another control scheme of an
exemplary embodiment of the present invention is illustrated. Here
the self-contained flexible volume compensator is shown disposed
around the housing defining the first and second chambers. In this
embodiment, a bypass valve 80 as an override (bypass) feature for
emergency operation when power fails, or service operation as
required. When power failure occurs, the bypass valve can be
opened, manually or by system setting and the chambers within the
cylinder and the self-contained volume compensator are connected
and fluid can flow through valves when driven manually. The system,
thus, can be driven manually. In this embodiment, the valve system
also comprises a plurality of counterbalance valves 82, check
valves 84 and pilot check valves 86.
[0053] FIGS. 6-8 illustrate alternative configurations wherein the
self-contained flexible volume compensator is located in various
positions within the housing. FIG. 9 illustrates a vehicle lift
gate being operated by a hydraulic actuator in accordance with an
exemplary embodiment of the present invention. In accordance with
an exemplary embodiment of the present invention the hydraulic
actuator may be secured between a door and body of a vehicle in two
ways, either the rod is secured to the door and the motor housing
end is secured to the body of the vehicle, or the rod is secured to
the body and the motor housing end is secured to the door of the
vehicle.
[0054] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the present
application.
* * * * *
References